Steer-By-Wire to Reach Production Vehicles

Taking a page from the world of aviation, Nissan Motor Co. plans to enter the "by-wire" world and control the steering of a future Infiniti vehicle with electronic signals.

The decision to bring steer-by-wire to a production vehicle is a major one for the automobile industry because it lays the foundation for eventual elimination of the mechanical components that now connect the driver to a vehicle's tires.

"There are a lot of advantages to this," Infiniti spokesman Kyle Bazemore told Design News. "It enhances the driving experience. And in the future, after consumer acceptance of the technology, we could theoretically do away with the mechanicals and save the weight."

Nissan's next-generation steering employs a steering angle sensor at the steering wheel, three ECUs for control, electric motors to power the rack, and a steering force actuator near the driver to retain the vehicle's "steering feel."

The next-generation steering system, as Nissan calls it, works by endowing the steering wheel with sensors that read the desired steering angle. Data from the sensors is sent to one of three electronic control units (ECUs), which activate electric motors on the vehicle's steering rack. In contrast, conventional steering uses a direct mechanical connection to the rack-and-pinion.

In truth, the new Nissan system won't eliminate the mechanical connection to the driver. Instead, it will use the mechanical connection as a redundant system, only in cases of extreme emergency. If, for example, a power supply conks out or all of the ECUs fail, it will employ a back-up clutch to mechanically connect the steering wheel to the tires. "The clutch is disengaged 999,999 times out of a million," Bazemore told us. "But the steering shaft is still there, just in case."

Nissan said steer-by-wire will enhance the driving experience. When it reaches the market late next year, it will eliminate some of the vibration from rough road surfaces and it will minutely adjust tire angles to compensate for crosswinds and sloped surfaces. At the same time, it will enable drivers to "feel" the road. Grip information, such as slipperiness, will be transferred back to a steering force actuator that will allow the steering wheel to retain some of its original feel. "Theoretically, you could have no steering feel at all, but that would not be good for drivers," Bazemore said. "That's why we dialed some -- but not all -- of the steering feel back into the system."

Today I drive a car with mechanical linkage and electric power boost (by chance, also a Nissan). Nissan propose to give me the same, with an extra sensor and wire to the steering mechanism. The electrical signal will be the primary mechanism, but so what? It doesn't replace the existing linkage. Its extra - extra weight, extra power, extra complexity. What happened to "keep it simple" ? Keeping the mechanical linkage in place as a backup is Nissans' way of saying "we like the new system - but we don't fully trust it"

I think the only down side is the number of automobiles on the road. The chances of the system failing are far greater than with cars. You cannot guarantee that the car is professionally maintained. However, if this system is fool proof, I mean that with masses in mind, then it is the future.

Right, Rob. For now, the clutch is there, but Nissan told us that if the mechanicals were ever removed, its engineers would incorporate a fail-safe sub-system. At this point however, it's not clear how the fail-safe sub-system would work.

Greg, the backup is absolutely required. While it is rare, I have been in a car where the power failed and the power steering stopped working. This was a hydralic system, and it was very hard to steer the car, but at least it could be done. Electrical systems are more likely to go out on a car, I would venture to guess, than the purely mechanical ones. Especially electrical systems that are digital.

A few weeks ago, Ford Motor Co. quietly announced that it was rolling out a new wrinkle to the powerful safety feature called stability control, adding even more lifesaving potential to a technology that has already been very successful.

A well-known automotive consultant who did an extensive teardown of BMW’s i3 all-electric car said its design is groundbreaking in multiple ways. “We’ve torn down about 450 cars, and we’ve never analyzed anything like this before.”

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